Current Pressure Swing Absorption (“PSA”) systems generally utilize molecular sieve material, such as zeolite, to separate incoming air from an air source, such as engine bleed air of an aircraft, by adsorbing nitrogen from the bleed air while allowing oxygen to pass therethrough. The separated oxygen may then be ultimately directed to specific areas (e.g., cockpit, cabin) and personnel (e.g., pilot, crew, passengers) aboard the aircraft so as to provide a breathable gas. The adsorbed nitrogen may be periodically purged from the zeolite under reduced pressure (e.g., at ambient pressure) by using pressure swing techniques in a known manner. The purged nitrogen is then either dumped overboard or used for other purposes, such as inerting the fuel tank ullage of the aircraft.
However, the material used in the molecular sieve beds degrades over time, especially when exposed to moisture or contaminants in the supply air. One problem encountered in the art is determining how much the sieve has degraded so as to allow proper and timely maintenance actions to recharge or replace a bed unit. This problem is especially true in regard to aircraft On Board Oxygen Systems (“OBOGS”). For OBOGS systems, it has been necessary to provide a known demand on the PSA oxygen concentrator, then measure the oxygen concentration produced and compare it to desired oxygen concentration levels. This approach, however, leads to several problems. For instance, it is difficult to do this on the aircraft without special actions such as valves controlling output flow rate and controlled inlet pressure conditions. These additional activities do not fit well with routine maintenance monitoring and add cost and complexity to operation of the aircraft. They also do not provide the necessary timely information about the health of the sieve material for each flight.
Thus, what is needed is a system and method for monitoring the health of the molecular sieve beds within a PSA system which does not require special actions or cumbersome flow control protocols.